1. Field of the Invention
The present invention relates generally to probe needles used in a probing apparatus for probing devices under test and more particularly, to a probe needle having enhanced current withstanding capacity and prolonged lifespan and a probe module using the same.
2. Description of the Related Art
FIGS. 1-2 show a conventional vertical probe module 10 comprising an upper die 11, a lower die 12 corresponding in location to the upper die 11, and a plurality of vertical probe needles 13 of buckling type arranged in between the upper and lower dies 11 and 12. The upper die 11 has a plurality of upper guide holes 112 through which the heads 132 of the probe needles 13 are respectively inserted, and the lower die 12 has a plurality of lower guide holes 122 through which the tails 134 of the probe needles 13 are respectively inserted. By press working, the body 136 of each probe needle 13 is press-formed from a section of a cylindrical post into a flat buckling shape in a way that a stop portion 138 having a maximum width greater than the diameter of the lower guide hole 122 is formed at the joint between the body 136 and the tail 134 for being stopped at the top surface of the lower die 12. When the tails 134 of the probe needles 13 are pressed on pads of a device under test, the bodies 136 of the probe needles 13 will deform in a same, fixed direction due to the flat buckling configuration of the bodies 136, such that a stable contact force may be provided by the tail 134 of each probe needle 13 to the pad of the device under test.
To meet the testing requirement of small-sized electronic devices, the conventional probe module has to be developed with a small pitch between each two adjacent probe needles. For accomplishing the goal of small pitch or fine pitch, one approach that can be adopted is to reduce the distance between two adjacent probe needles, and the other is to make the probe needles having a relatively smaller diameter than that of the conventional ones. Referring to FIG. 3, if the pitch P between two adjacent probe needles 13, i.e. the distance from a side edge of one probe needle to the corresponding side edge of the other probe needle or the center-to-center distance between the two adjacent probe needles, is reduced under the condition that the diameter of the probe needles remains unchanged, the risk of short circuit may increase because the flat buckling bodies 136, especially the upper sections of the flat buckling bodies 136, tend to be unintentionally contacted with each other when they are deformed upon receiving external force. On the other hand, if the probe needles 13 are press-made from cylindrical posts having a relatively smaller diameter than the conventional ones to enable that the probe needles 13 can be arranged in a relatively smaller pitch within a safety range, the current withstanding capacity of the probe needles may however drop down to adversely affect the lifespan of the probe needles.